This invention relates to an optical semiconductor device. Property of the optical semiconductor device is influenced by temperature. Therefore, improvement for decreasing thermal affect is required.
Conventionally, face-down mounting is one of the methods for mounting an optical semiconductor device. A surface electrode of the optical semiconductor device is turned face down, and the device is mounted onto a basement such as a heat sink.
According to the face-down mounting, comparing with face-up mounting where the surface electrode is turned face up, distance between an active layer of the optical semiconductor device and a heat sink is short. Therefore, heat of the active layer of the device is diffused easily to the heat sink, and, it is possible to improve properties of the optical semiconductor device such as characteristic temperature or maximum output property.
In mounting the optical semiconductor device such as a laser diode, electrode layer is formed on the laser diode by vacuum evaporation, and solder layer is formed on the heat sink. Then, the electrode layer of the laser diode is contacted to the solder. Melting the solder, the laser diode is stuck on the heat sink.
In a kind of optical semiconductor device, one pair of facets of the active layer are covered with insulating layer such as reflecting film or non-reflecting film, therefore those facets are protected electrically, but other pair of facets are exposed. When such kind of device is mounted on the heat sink by the face-down mounting, solder reaches the exposed facets of the active layer. It occurs an electrical short of the device.
On the other hand, to restrict spread of an electric current or an electric field, a narrow semiconductor mesa stripe is formed on the active layer. When an optical semiconductor device with the mesa stripe is mounted onto a mount base by face-down mounting, connection between the device and the mount base is not sure. Therefore, it is difficult to consistently manufacture the device with same properties.